This starter grant award to Texas A&M will support the research of Professor Cynthia M. Dupureur. The theme of the research is the relationship of structure and function in restriction enzymes. Studies focus on EcoRI restriction endonuclease. While the structure of the enzyme is known, the position and thus role of the N-terminal arm is crystallographically undefined. In this research, the relationships among the required N-terminal arm and the rest of the enzyme, metal ions, and substrate are investigated using peptide synthesis, spectroscopy, metal ion binding assays, and non-covalent reconstitution experiments. Information obtained leads to elucidation of the relationships among these reaction components, as well as to clarification of working models of EcoRI activity. This research will advance the fundamental understanding of restriction enzymes essential for development of chemotherapeutics that target nucleic acids.